Distilling alcohols in presence of amines



Unite States atent' 'Bernard H. Gwyun, Fawn Township, Allegheny County,

and Arthur C. Whitaker, Fox Chapel, Pa., assignors to Gulf Research &Development Company, Pittsburgh, Pa., a corporation of Delaware NDrawing. Application April 29, 1954 Serial No. 426,591

9 Claims. (Cl. 260-638) This invention relates to a process forpreventing decomposition of alcohols during their distillation andparticularly to a process for preventing decomposition of alcoholsproduced in the 0x0 process during their distillation.

In the preparation of alcohols, the final alcohol product obtained quiteoften contains some impurities that must first be removed from theproduct before an acceptable alcohol can be produced. These impuritiescan find their way into the alcohol product from several sources butchiefly from the reactants employed in the preparation of the alcoholproduct and the equipment used. The alcohol product can be purified toobtain a substantially pure alcohol by the relatively simple expedientof distillation. However, under some of the conditions employed in thedistillation of the alcohol product, particularly with respect to thetemperature, the impurities seriously interfere with satisfactoryoperation of the distillation stage and an appreciable amount of thealcohol is lost during the process.

This difficulty has been found to exist particularly in the distillationof alcohols produced in the Oxo process. Briefly, the Oxo processcomprises two stages for the production of alcohols. In the first stagealdehydes are synthesized, while in the second the aldehydes arehydrogenated to the corresponding alcohols.

The first stage of the 0x0 process, sometimes called thehydroformylation reaction stage, generally comprises reacting a mixturecomprising an olefin or olefins, hydrogen and carbon monoxide in thepresence of a hydroformylation catalyst at an elevated superatmosphericpressure, such as a pressure of about 1500 to about 4500 pounds persquare inch gauge, and an elevated temperature, such as a temperature ofabout 100 to about 600 F., to produce a hydroformylation or oxygenatedorganic product comprising chiefly aldehydes having one more carbon atomthan the original olefins and smaller amounts of alcohols, acetals, andother organic products. Thus, if heptenes are charged to thehydroformylation stage of an OX0 unit, octyl aldehydes are produced.

The hydroformylation product stream also contains, in addition to theproducts mentioned above, a catalytic metal carbonyl or small amounts ofacatalytic metalsalt of an organic acid. The catalytic metal isoriginally introduced into the hydroformylation reaction stage as thecarbonyl, or is converted to the carbonyl in the reaction zone. Cobaltor iron, generally in the form of an organic salt such as cobaltnaphthenate or the cobalt salt of Z-ethylhexanoic acid, is usuallyemployed as the catalytic metal.

' The walls of the hydroformylation reactor and the transfer lines usedin the hydroformylation stage are usually made of iron or its alloys.During the hydroformylation stage some of the metal in the walls of thehydroformylation reactor and transfer lines finds its way into thehydroformylation reaction product where it generally appears as a metalcarbonyl. In this way iron carbonyl is produced when the walls of thereactor and the transfer lines are constructed of iron and carbonyls ofalloying metals are also produced when the walls are constructed ofmetal "ice alloys. The alloying metal carbonyls, in addition to ironcarbonyl, usually comprise those of nickel, chromium, and molybdenum.

Since these metallic carbonyls seriously interfere with the subsequentreactions to which the hydroformylation reaction product is to besubjected, it is a common expedient to pass the hydroformylationreaction product to a demetalling zone wherein it is subjected to ademetalling treatment. This can be done in numerous ways but is oftenaccomplished by the application of heat to the hydroformylation reactionproduct to decompose the metal carbonyls and deposit the elemental metalresulting from such decomposition in the demetalling zone, preferably onan absorbent material such as pumice. While the demetalling step iseffective to remove substantially all of the hydroformylation catalystor its decomposition or reaction product from the hydroformylationreaction product, it is exceedingly diificult to remove completely thesesubstances from the hydroformylation reaction product, and hence theeffluent from the demetalling zone generally contains traces of thesesubstances.

The hydroformylation reaction product from the demetalling zone is thenpassed to the second or hydrogenation stage of the Oxo process where thealdehydes in the hydroformylation reaction product are hydrogenated tothe corresponding alcohol under hydrogenating conditions, e. g. atemperature in the range of about 300 to about 450 F. and a pressure inthe range of about 500 pounds to about 3000 pounds per square inch, inthe presence of a hydrogenation catalyst such as nickel or nickel oxide.Here, too, the catalytic material or its decomposition or reactionproducts appear in the eflluent from the hydrogenation stage, and it isextremely difficult to obtain an alcohol which does not contain at leasta trace of these impurities.

The alcohol product obtained from the second stage of the 0x0 processcomprises alcohols, traces of the hydroformylation and hydrogenationcatalysts, as well as their decomposition and reaction products as setforth above, some unreacted olefins and aldehydes, aldols, etc. In orderto purify this product and obtain the desired alcohol, the alcoholproduct is usually subjected to a distillation treatment. During thedistillation step, however, an appreciable amount of the alcohol isdecomposed with the result that the yield of pure alcohol obtained isreduced.

It is believed that the traces of catalytic metals and theirdecomposition and reaction products from the two stages of the Oxoprocess which are present in the alcohol product act as catalyst for thedecomposition of the alcohol under the distillation conditions employed.Initially, the alcohol is probably dehydrogenated to the correspondingaldehyde. This aldehyde is believed to be further decomposed to a normalhydrocarbon by the release of carbon monoxide and additionally condenseswith itself to form aldol condensation products.

We have discovered that alcohols containing impurities, particularlyalcohols obtained in the Oxo process, can be purified by distillationand the amount of alcohol gen erally lost thereby can be substantiallyreduced by conducting the distillation process in the presence of anadditive which will not boil out but will remain in the distillationmixture at the distillation temperature throughout the distillationstage and which will render the impurities unreactive and non-catalytictoward the decomposition reaction at distillation temperatures.

Included among the groups of compounds which we have found to beparticularly effective in the practice of our invention are any amineswhich .will not boil out but will remain in the distillation mixture atthe temperature employed in distilling the alcohol, particularlyaliphatic amines having a total of 2 to about 20 carbon atoms in 3 themolecule and aromatic amines having a total of about 6 to about 20carbon atoms in the molecule. Examples of amines which can be usedinclude primary amines 4 ture of about 180 C. and atmospheric pressurefor about 24 hours to simulate commercial plant operation. The resultsof these runs are tabulated below in Table 1.

such as hexylamine and octadecylamine; polyamines such astriethylenetetramine, ethylenediamine, diethylenetriamine,tetraethylenepentamine, and propylenediamine; hydroxyamines such asethanolamine, diethanolamine, and isopropanolamine; and aromatic aminessuch as diphenylamine and monoethylaniline. It is believed that theseamines act in one of two ways to render the impurities present in thealcohol product non-catalytic toward the decomposition of alcohols whichis susceptibleof taking place during the distillation stage. a When theimpurity is present in elemental form as the metal, for example ascobalt, nickel, iron, etc., the amine is believed to form a coatingabout the metal and thus renders it inefiec tive as catalyst. In caseswhere the impurity is present in ionizable form, for example as a saltsuch as the cobalt salt of 2-ethylhexanoic acid, we believe the amineforms with the impurity present a Werner-type complex stable at thedistillation temperatures to be employed and boiling at a temperatureabove the boiling point of the alcohol.

Since only traces of the impurities or catalytic material are present inthe alcohol product to be distilled,.only very small amounts of thesubstances defined above or combinations thereof need be added theretoprior to distillation in order to'render the impurities unreactive andnon-catalytic toward the decomposition of the alcohol. Accordingly,while large amounts of the additives can be employed with good efiect,in general we prefer to employ above about 0.05, preferably betweenabout 0.1 to about 0.5, weight percent of the additive, based upon theweight of the alcohol product to be treated.

While our invention can be employed in the purification by distillationof mixtures containing alcohols of any kind, it is particularlyapplicable to the treatment of alcohols boiling above about 100 C. sincedecomposition of alcohols is not a serious problem with those havingboiling points below about 100 C., for example ethyl alcohol. Thisinvention has been found to be especially elfective indistilling analcohol product obtained from the x0 process and comprising isooctylalcohol and the catalytic impurities noted above. I

This invention can best be illustrated by reference to severaldistillation runs which were made on alcohol products containing variousamounts of impurities capable of acting as catalyst during thedistillation, as well as alcohol products containing in additioncompounds capable of rendering the impurities ineffective as catalysts.In each of the runs, 200 grams of isooctyl alcohol was used. Raneynickel as an impurity Was present in an amount of 2 /2 percent by weight(5 grams), while the iron, nickel and cobalt salts of 2-ethylhexano icacid were present in an amount of 5 percent by weight grams), The amountof additive incorporated in the alcohol product in each instance was 2percent by weight (5 grams). The alcohol product was refluxed anddistilled at a tempera- The data in Table 1 clearly show the markedimprovement obtained in the distillation of an alcohol productcontaining impurities in accordance with our invention. In the case ofalcohols containing a metal salt of an organic acid as impurity, itshould be noted that when the alcohol containing the nickel salt of2-ethylhexanoic acid as impurity was distilled, 39.3 percent by weightof residue (polymers due to'aldol condensation and alcohol decompositionproducts, as well as impurities originally in the alcohol product)resulted. The addition of a relatively small amount oftriethylenetetramine to this alcohol cut the loss by about percent,specifically down to 3.0 percent by weight. 'It will be seen that theaddition of a small amount of additive to an alcohol containing Raneynickel as an impurity resulted in a decrease of residue from 10.1 to 3.0percent by weight. In addition, in the distillation of the alcoholcontaining Raney nickel as impurity but no additive, 19.1'percent byweight. of the original product was lost during the reaction as carbonmonoxide, hydrogen, water vapor and heptane, and 5.7 percent by weightof material boiling. below C alcohol remained behind, probably heptaneretained in the condenser system and unreacted aldehyde. The addition ofthe additive to the alcohol containing Raney nickel as impurity resultedin a substantial decrease of material lost during the reaction as wellas material boiling below C alcohol. In the former, after the addition,the amount lost during the reaction was but 3.3 percent by weight, whilein the latter only 0.3 percent by weight of material boiling below Calcohol remained. Similar improvements were obtained in this respectwith the addition of triethylenetetramine to the alcohol containing thenickel salt as impurity.

Obviously, many modifications and variations of the invention, ashereinabove set forth, can be made without departing from the spirit andscope thereof, and therefore only such limitations should be imposed asare indicated in the appended claims.

We claim:

1. A process for preventing the decomposition during 'itsdistillation-of an alcohol product containing metallic impurities whichcomprises incorporating therein, prior to distillation, an amineselected from the group consisting of primary and secondary aliphaticamines having a total of 2 to about 20 carbon atoms in the molecule andprimary and secondary aromatic amines having a total of about 6 to about20 carbon atoms in the molecule which will not boil out butwill remainin the distillation mixture at the distillation temperature throughoutthe distillation stage and which will render said impurities unreactiveand non-catalytic toward decomposition of the alcohol, and thereafterdistilling said alcohol product. 2. A process for preventing thedecomposition during 'its' distillation of an alcohol product obtainedin the 0x0 process comprising an alcohol and metallic impurities whichcomprises incorporating therein, prior to distillation, an amineselected from the group consisting of primary and secondary aliphaticamines having a total of 2 to about 20 carbon atoms in the molecule andprimary and secondary aromatic amines having a total of about 6 to about20 carbon atoms in the molecule which will not boil out but will remainin the distillation mixture at the distillation temperature throughoutthe distillation stage and which will render said impurities unreactiveand non-catalytic toward decomposition of the alcohol, and thereafterdistilling said alcohol product.

3. A process for preventing the decomposition during its distillation ofan alcohol product obtained in the 0x0 process comprising an alcohol andmetallic impurities which comprises incorporating therein, prior todistillation, a polyamine which will not boil out but will remain in thedistillation mixture at the distillation temperature throughout thedistillation stage, and thereafter distilling said alcohol product.

4. A process for preventing the decomposition during its distillation ofan alcohol product obtained in the Oxo process comprising an alcohol andmetallic impurities comprising nickel which comprises incorporatingtherein, prior to distillation, triethylenetetramine, and thereafterdistilling said alcohol product.

5. A process for the production of alcohols which comprises reacting amixture comprising an olefin, carbon monoxide and hydrogen in thepresence of a metallic hydroformylation reaction catalyst at an elevatedsuperatmospheric pressure and elevated temperature to obtain ahydroformylation reaction mixture comprising an aldehyde, saidhydroformylation catalyst and its decomposition and reaction products,treating said hydroformylation reaction product to remove substantiallyall of said hydroformylation catalyst and its decomposition and reactionproducts therefrom, reacting said latter treated product underhydrogenating conditions in the presence of a nickel hydrogenationcatalyst to obtain an alcohol product comprising alcohols and smallamounts of hy droformylation and hydrogenation catalysts and theirreaction and decomposition products as impurities, incorporating in saidalcohol product, prior to distillation, an amine selected from the groupconsisting of primary and secondary aliphatic amines having a total of 2to about 20 carbon atoms in the molecule and primary and secondaryaromatic amines having a total of about 6 to about 20 carbon atoms inthe molecule which will not boil out but will remain in the alcoholproduct at the distillation temperatures to be employed in distillingsaid alcohol product and will render said impurities unreactive andnon-cata- 6 lytic toward decomposition of the alcohol, and thereafterdistilling said latter product to obtain alcohol.

6. A process for the production of alcohols which comprises reacting amixture comprising an olefin, carbon monoxide and hydrogen in thepresence of a metallic hydroformylation reaction catalyst at an elevatedsuperatmospheric pressure and elevated temperature to obtain ahydroformylation reaction mixture comprising an aldehyde, saidhydroformylation catalyst and its decomposition and reaction products,treating said hydroformylation reaction product to remove substantiallyall of said hydroformylation catalyst and its decomposition and reactionproducts therefrom, reacting said latter treated product underhydrogenating conditions in the presence of a hydrogenation catalystcomprising nickel to obtain an alcohol product comprising alcohols andsmall amounts of hydroformylation and hydrogenation catalysts and theirreaction and decomposition products, incorporating in said alcoholproduct a polyamine having a total of about 2 to about 20 carbon atomsin the molecule which will not boil out but will remain in thedistillation mixture at the distillation temperature throughout thedistillation stage, and thereafter distilling said latter alcoholproduct.

7. A process as in claim 6 wherein the amine is triethylenetetramine.

8. A process as in claim 6 wherein the catalyst is an organic cobaltsalt and the amine is triethylenetetramine.

9. A process as in claim 6 wherein the olefin is heptene, the metallichydroformylafion catalyst is an organic cobalt salt and the amine istriethylenetetramine.

References Cited in the file of this patent UNITED STATES PATENTS1,847,711 Calcott Mar. 1, 1932 1,987,601 Burke Jan. 15, 1935 1,992,689Cox Feb. 26, 1935 2,139,179 Tulleners Dec. 6, 1938 2,143,478 Engs et alJan. 10, 1939 2,227,485 Bump Jan. 7, 1941 2,352,164 Burnham June 27,1944 2,441,848 Sexton May 18, 1948 2,441,849 Sexton May 18, 19482,570,403 Stevens et a1 Oct. 9, 1951 2,614,072 Carlson et al Oct. 14,1952 2,631,970 Barnes Mar. 17, 1953 2,635,074 Steitz Apr. 14, 19532,648,694 Mason Aug. 11, 1953 FOREIGN PATENTS 494,985 Great Britain Nov.4, 1938

5. A PROCESS FOR THE PRODUCTION OF ALCOHOLS WHICH COMPRISES REACTING AMIXTURE COMPRISING AN OLEFIN, CARBON MONOXIDE AND HYDROGEN IN THEPRESENCE OF A METALLIC HYDROFERMYLATION REACTION CATALYST AT AN ELEVATEDSUPERATMOSPHERIC PRESSURE AND ELEVATED TEMPERATURE TO OBTAIN AHYDROFORMYLATION REACTION MIXTURE COMPRISING AN ALDEHYDE, SAIDHYDROFORMYLATION CATALYST AND ITS DECOMPOSITION AND REACTION PRODUCTS,TREATING SAID HYDROFORMYLATION REACTION PRODUCT TO REMOVE SUBSTANTIALLYALL OF SAID HYDROFORMYLATION CATALYST AND ITS DECOMPOSITION AND REACTIONPRODUCTS THEREFROM, REACTING SAID LATTER TREATED PRODUCT UNDERHYDROGENATING CONDITIONS IN THE PRESENCE OF A NICKEL HYDROGENATIONCATALYST TO OBTAIN AN ALCOHOL PRODUCT COMPRISING ALCOHOLS AND SMALLAMOUNTS OF HYDROFORMYLATION AND HYDROGENATION CATALYSTS AND THEIRREACTION AND DECOMPOSITION PRODUCTS AS IMPURITIES, INCORPORATING IN SAIDALCOHOL PRODUCT, PRIOR TO DISTILLATION, AN AMINE SELECTED FROM THE GROUPCONSISTING OF PRIMARY AND SECONDARY ALIPHATIC AMINES HAVING A TOTAL OF 2TO ABOUT 20 CARBON ATOMS IN THE MOLECULE AND PRIMARY AND SECONDARYAROMATIC AMINES HAVING A TOTAL OF ABOUT 6 TO ABOUT 20 CARBON ATOMS INTHE MOLECULE WHICH WILL NOT BOIL OUT BUT WILL REMAIN IN THE ALCOHOLPRODUCT AT THE DISTILLATION TEMPERATURES TO BE EMPLOYED IN DISTILLINGSAID ALCOHOL PRODUCT AND WILL RENDER SAID IMPURITIES UNREACTIVE ANDNON-CATALYTIC TOWARD DECOMPOSITION OF THE ALCOHOL, AND THEREAFTERDISTILLING SAID LATTER PRODUCT TO OBTAIN ALCOHOL.